JPH1018075A - Electrolytic copper foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide double treat copper foil free from the problems of heat resistance and discoloration, particularly, copper foil for the internal layer of a multilayer printed wiring board. SOLUTION: A glossy face is provided with a roughening treated layer composed of a Cu-Ni allay or a Cu-Co-Ni alloy. The roughened face is provided with a coating layer composed of a Cu-Zn alloy, and preferably, at least one side is furthermore provided with a Cr base rust preventing layer. The copper foil is suitable particularly for the use as electrolytic copper foil for the internal layer of a multilayer printed wiring board. The surface roughness of the glossy face is preferably regulated to 0.05 to 0.2μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing Cu-N
It relates to an electrolytic copper foil characterized by having a roughened layer made of an i-alloy or a Cu-Co-Ni alloy,
In particular, the present invention relates to an electrolytic copper foil suitable for use as an electrolytic copper foil for an inner layer of a multilayer printed wiring board.

[0002]

2. Description of the Related Art Copper and copper alloy foil (hereinafter referred to as copper foil)
Has greatly contributed to the development of the electrical and electronic related industries,
In particular, it is indispensable as a printed circuit material. In general, copper foil for printed circuits is laminated and bonded to a base material such as a synthetic resin board and a film under a high temperature and a high pressure with an adhesive or without using an adhesive to produce a copper-clad laminate. After a necessary circuit is printed through a resist coating and exposure process to form a circuit to be formed, an etching process for removing an unnecessary portion is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices. The quality requirements for the copper foil for printed circuit boards differ between the surface to be bonded to the resin substrate and the non-contact surface, and many methods have been proposed for each.

[0003] Copper foils are classified into electrolytic copper foils and rolled copper foils. Most of copper foils used for printed wiring boards are electrolytic copper foils from the viewpoint of adhesive strength. Electrodeposited copper foil is made from electrolytic copper or electric wire scrap with a purity equivalent to that, and it is dissolved in an aqueous sulfuric acid-acidic copper sulfate solution to prepare an electrolytic bath.The surface is usually made of stainless steel, titanium, chrome plating, etc. The formed cathode cylinder is leveled, an electrolytic solution is passed between the cathode and the anode arranged opposite to the cathode, a current is passed between the anode and the anode while rotating the cathode, and copper is applied to the surface of the cathode. After electrodeposition, the electrodeposit having a predetermined thickness is continuously peeled off to produce a copper foil (called a raw foil). The thickness of the copper foil is
This is performed by adjusting the magnitude of the current and the rotation speed. After that, depending on the quality requirements for the copper foil for printed circuit boards, many processes are performed on the surface to be bonded to the resin substrate (hereinafter referred to as a roughened surface) and the non-bonded surface (hereinafter referred to as a glossy surface). Done. This is called a treatment (surface treatment) step. Although the electrolytic copper foil has irregularities at the time of production, the roughened surface has a thickness of 0.2 to 3 μm for improving the peel strength with the substrate.
Generally, about m copper particles (also referred to as roughened particles) are adhered. The copper particles enhance the projections of the electrolytic copper foil to further increase the irregularities. To prevent copper particles from falling off,
In some cases, a thin copper plating layer is formed to cover the copper particle layer. This is called a roughening process.

[0004] As a method of manufacturing a copper-clad laminate, a hot press method or a continuous method has recently been adopted. For example, taking the production of a paper-based phenolic resin copper-clad laminate by a hot press method as an example, a prepreg is produced by synthesizing a phenolic resin, impregnating and drying the phenolic resin on the paper substrate, and finally, A predetermined number of prepregs and copper foils are combined, hot-pressed by a multi-stage press, unsealed, trimmed, and sent to the next step. In the case of the continuous method, a single-sided copper-clad laminate and a double-sided copper-clad laminate are manufactured. For example, in the case of a paper-based polyester resin copper-clad laminate, the base paper is unwound from a plurality of roll-shaped base papers, each separately undergoes a paper treatment, a resin impregnation step, and a plurality of resin-impregnated papers are laminated by a roll pair. You. Next, a copper foil that has undergone an adhesive application step, or in the case of one side, a copper foil and a carrier are laminated. The product thickness is controlled in the laminating and laminating steps. Next, it is sent to the curing furnace, where the curing reaction of the resin occurs,
To cure. After curing, the product undergoes a fixed-size cutting, after-curing and end-face polishing steps, and is further subjected to appearance inspection and characteristic inspection to obtain a product. The difference between single-sided and double-sided
The carrier film is drawn out from below, and after curing the resin, the carrier is peeled off and rolled up, whereas in the case of both sides, the copper foil that has passed through the adhesive application step is also drawn out from below, and the other steps are also for one side. Both sides are equivalent. Others
A glass-epoxy resin substrate and the like are manufactured in a similar process.

[0005] Further, as the number of input / output terminals, that is, the number of pins increases remarkably as the elements become more highly integrated. In addition, due to the demand for smaller and more compact devices and the need for more sophisticated systems, printed wiring boards are required. Are progressing to multilayering. In the case of manufacturing a multilayer printed wiring board, an outer layer circuit board or copper foil is laminated via a prepreg on an inner layer circuit board on which a circuit is formed with copper foil on one side and / or both sides,
This is generally manufactured by forming a laminate by pressing and laminating a circuit board for an inner layer and a circuit board for an outer layer or a copper foil via an insulating layer made of a resin-impregnated base material.

[0006] In order to improve the adhesive strength by multi-layer molding, a surface treatment is performed to physically or chemically treat the surface of the inner copper foil to improve the adhesive strength between the copper foil surface and the prepreg. This is called inner layer roughening. Until now, as the inner layer roughening treatment, blackening treatment has been mainly performed. For the blackening treatment, 31 g / l of sodium hydrochloride-15 g / l of sodium hydroxide-12 g / l of trisodium phosphate solution or 60 g / l of sodium hydrochloride-8 g / l of sodium hydroxide-10 g / l Using a blackening treatment solution represented by trisodium phosphate solution of
Minutes and in the latter at 95-98 ° C. for 1 minute, C
u ₂ O (red) and CuO (black) are deposited on the copper foil surface as a mixture. The blackening treatment has good stability in mass production and is excellent in adhesive strength and heat resistance, but is easily attacked by acid, especially hydrochloric acid, and dissolves the oxide film. This is called a haloing phenomenon, and causes a decrease in adhesive strength. Therefore, when performing the blackening treatment, it is necessary to use a salt type predip catalyst. In addition, if the treatment method is inappropriate, a rough and sponge-like oxide film is easily generated. Because the blackening treatment is a treatment with a high temperature alkaline solution,
If the epoxy or polyimide resin swells and the inner layer material is thin, it affects the dimensional stability, so care must be taken in the liquid concentration, temperature and immersion time.

[0007]

In view of the above-mentioned drawbacks of the blackening treatment, as another method, the use of double-treat (DT) copper foil having both surfaces treated with electrolytic copper foil has been increasing in recent years. As described above, the electrolytic copper foil has irregularities at the time of manufacture, but on the roughened surface, the convexities of the electrolytic copper foil are strengthened to improve the peel strength with the substrate, and the irregularities are further increased. Generally, copper particles of about 0.2 to 3 μm are adhered, and a roughening process of forming a thin copper plating layer over the copper particle layer is performed to prevent the copper particles from falling off. The double-treated copper foil has been subjected to the same roughening treatment on the glossy surface as on the roughened surface.

[0008] However, it has been recognized that the current double-treated copper foil does not have good heat resistance, and that it is significantly discolored by aging. Therefore, an object of the present invention is to provide a double-treated copper foil, particularly a copper foil for an inner layer of a multilayer printed wiring board, having no problems such as heat resistance and discoloration.

[0009]

Means for Solving the Problems The present inventor has proposed that a glossy surface of a double-treated copper foil be made of a Cu-Ni alloy or Cu-Co-N
It has been found that by providing a roughening layer made of an i-alloy, problems such as heat resistance and discoloration during aging can be significantly reduced. Cu-Ni alloy or Cu-C
The roughening layer made of an o-Ni alloy is known as a roughening method for a rolled copper foil, but has not been applied to the glossy surface of a double-treat electrolytic copper foil. Any known roughening treatment can be applied to the roughened surface of the double-treated electrolytic copper foil, but it is preferable to provide a coating layer made of a Cu-Zn alloy. Further, it is preferable to further provide a Cr-based antirust layer on at least one surface.

[0010] Thus, the present invention provides (1) a method in which Cu is added to a glossy surface;
An electrolytic copper foil provided with a roughening treatment layer made of a -Ni alloy or a Cu-Co-Ni alloy, and (2) a coating layer made of a Cu-Zn alloy provided on a roughened surface. And (3) an electrolytic copper foil according to (1) or (2), further comprising a Cr-based antirust layer on at least one surface. The copper foil of the present invention is particularly suitable for use as an electrolytic copper foil for an inner layer of a multilayer printed wiring board. The glossy surface preferably has a surface roughness of 0.05 to 0.2 μm. If it is less than 0.05 μm, the adhesive strength is not sufficient, and if it exceeds 0.2 μm, it becomes difficult to form a fine pattern circuit.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a double-treat (DT) electrolytic copper foil is obtained by roughening both surfaces of an electrolytic copper foil. Electrolytic copper foil has irregularities on the roughened surface opposite to the cathode side at the time of manufacturing, but on the roughened surface, increase the convex part of the electrolytic copper foil to improve the peeling strength with the substrate Generally, copper particles of about 0.2 to 3 μm are adhered to further increase the unevenness. In order to prevent the copper particles from falling, a rough copper plating layer is formed by covering the copper particle layer. Processing is in progress. At present, the double-treated electrolytic copper foil is subjected to the same roughening treatment on the glossy surface as on the roughened surface. According to the present invention, Cu-
A roughening layer made of a Ni alloy or a Cu-Co-Ni alloy is formed.

A general bath for forming a Cu—Ni alloy as a roughening treatment for a glossy surface of an electrolytic copper foil in the present invention is as follows:
It is as follows: (copper-nickel alloy plating) Cu: 5 to 10 g / liter Ni: 10 to 20 g / liter pH: 1 to 4 Temperature: 20 to 40 ° C. Current density D _k : 10 to 30 A / dm ² hours : 2 to 5 seconds Copper-nickel alloy plating has an adhesion amount of 15 to 40 mg / dm ² copper-100 to 900 μg / d by electrolytic plating.
Implemented to form a binary alloy layer such as m ² nickel. If the amount of Ni attached is less than 100 μg / dm ² , the heat resistance becomes poor. On the other hand, the Ni adhesion amount is 900
If it exceeds μg / dm ² , the etching residue increases. However, when the Ni adhesion amount exceeds 500 μg / dm ² , the etching property tends to decrease. That is, it is not at a level that an etching residue can be formed or cannot be etched, but it is difficult to form a fine pattern. A preferable nickel deposition amount is 200 to 400 μg / dm ² .

The general bath and plating conditions for forming the ternary copper-cobalt-nickel alloy plating are as follows: (copper-cobalt-nickel alloy plating) Cu: 10-20 g / liter Co: 1 Ni: 1 to 10 g / liter pH: 1 to 4 Temperature: 40 to 50 ° C. Current density D _k : 20 to 30 A / dm ² hours: 1 to 5 seconds

The copper-cobalt-nickel alloy plating has a coating amount of 15 to 40 mg / dm ²
100-3000 μg / dm ² cobalt-100-90
It is performed to form a ternary alloy layer such as 0 μg / dm ² nickel. Co adhesion amount is 100 μg / d
If it is less than m ² , the heat resistance will deteriorate and the etching properties will deteriorate. If the Co deposition amount exceeds 3000 μg / dm ² , it is not preferable when the influence of magnetism must be considered,
Etching spots may occur and acid and chemical resistance degradation may be considered. If the amount of Ni attached is less than 100 μg / dm ² , the heat resistance becomes poor. On the other hand, when the Ni adhesion amount is 9
If it exceeds 00 μg / dm ² , the etching residue increases. However, when the Ni adhesion amount exceeds 500 μg / dm ² , the etching property tends to decrease. That is, it is not at a level that an etching residue can be formed or cannot be etched, but it is difficult to form a fine pattern. The preferred Co coverage is 2000-3000 μg / dm ² and the preferred nickel coverage is 200-400 μg.
g / dm ² . Here, the etching stain means that when etched with copper chloride, Co remains without dissolving, and when the etching residue is alkali-etched with ammonium chloride, Ni remains without dissolving. It means that.

On the other hand, for the purpose of improving the peel strength, the roughened surface of the copper foil is usually subjected to a roughening treatment for performing electrodeposition in the form of copper or copper oxide bumps. Such knob-like electrodeposition is easily brought about by so-called burnt electrodeposition. General bath for performing roughening treatment to the roughened surface are as follows: (a copper - arsenic alloy plating) Cu: 10 to 50 g / l H ₂ SO _4: 50~150g / l As: 1 to 10 g / Liter Temperature: 20 to 40 ° C Current density: 10 to 100 A / dm ² hours: 1 to 5 seconds A coating layer made of a Cu—Zn alloy (brass) is formed on the roughened surface subjected to the above roughening treatment. . The electrolysis conditions of the brass plating are as follows: (copper-zinc alloy plating) NaCN: 10 to 30 g / liter NaOH: 40 to 100 g / liter Cu: 60 to 120 g / liter Zn: 1 to 10 g / liter Temperature: 60 -80 ° C Current density: 1-10 A / dm ² hours: 1-10 seconds In this case, when laminated on a resin base material, there is almost no stain on the resin layer, and there is little deterioration in peel strength after high-temperature heating. It is important to form a coating layer made of brass having a zinc content of 30% or less at an electric quantity of 30 As / dm ² or more in order to completely prevent the circuit erosion phenomenon without lowering the electric current. Even if the amount of electricity is 30 As / dm ² or more, the circuit erosion cannot be avoided if the zinc content exceeds 30%, and if the amount of electricity is less than 30 As / dm ² , regardless of the zinc content, the circuit erosion occurs. Cannot be completely prevented. That is, electric quantity 30 As / dm
Unless both the conditions of ² or more and zinc content of 30% or less are not satisfied, the circuit erosion phenomenon cannot be completely prevented. When the amount of electricity is 30 As / dm ² or more,
Although the lower limit of the zinc content is not particularly limited, the zinc content is 15% or more, preferably 20% or more when comprehensively determined taking into account characteristics other than circuit erosion prevention (eg, heat resistance). It is desirable that

Thereafter, at least one surface of the copper foil is subjected to a rust prevention treatment as required. The preferred rust preventive treatment in the present invention is a Cr-based rust preventive treatment, which includes a coating treatment of chromium oxide alone or a mixture of chromium oxide and zinc / zinc oxide, including immersion chromate treatment and electrolytic chromate treatment. is there. The coating treatment of a mixture of chromium oxide and zinc / zinc oxide refers to zinc-containing zinc or zinc oxide and chromium oxide by electroplating using a plating bath containing zinc salt or zinc oxide and chromate. This treatment covers the rust-preventive layer of the chromium-based mixture. As the plating bath, typically, at least one of dichromates such as K ₂ Cr ₂ O ₇ and Na ₂ Cr ₂ O ₇ and CrO ₃ and a water-soluble zinc salt such as Zn
A mixed aqueous solution of at least one of O ₂ , ZnSO ₄ .7H ₂ O, and an alkali hydroxide is used. A typical Cr-based anti-rust plating bath composition and examples of electrolysis conditions are as follows: (Chromium anti-rust treatment 1): K ₂ Cr ₂ O ₇ (or Na ₂ Cr ₂ O ₇ , CrO)
₃ ): 0.2 to 20 g / l Acid: phosphoric acid or sulfuric acid, organic acid pH: 1.0 to 3.5 Bath temperature: 20 to 40 ° C. Current density: 0.1 to 0.5 A / dm ² hours: 10-60 seconds anode: lead plates, Pt-Ti plate, stainless steel plate chromium oxide coating weight is sufficient 50 [mu] g / dm ² or less as the amount of chromium, and preferably from 15~30μg / dm ^2. If the amount of chromium exceeds 30 μg / dm ² , the rust-preventing power is improved, but the etching property is lowered. (Chromium anticorrosive treatment _{2) K 2 Cr 2 O 7} (Na 2 Cr 2 O 7 or CrO _3): 2~10g / liter NaOH or KOH: 10 to 50 g / liter ZnO or _{ZnSO 4 · 7H 2 O: 0} . PH: 7 to 13 Bath temperature: 20 to 80 ° C. Current density D _k : 0.05 to 5 A / dm ² hours: 5 to 30 seconds Anode: Pt-Ti plate, stainless steel plate, etc. Chromium oxide A coating amount of 15 μg / dm ² or more for chromium and 30 μg / dm ² or more for zinc is required.

The copper foil thus obtained is preferably
It has a surface roughness in the range of 0.05 to 0.2 μm. If the thickness exceeds 0.2 μm, the adhesive strength is increased, but it is not preferable for fine patterns, for example, etching residue is generated. If it is less than 0.05 μm, the adhesive strength will be weak.

The electrolytic copper foil according to the present invention has excellent heat-resistant peel strength, oxidation resistance and hydrochloric acid resistance, and has a black color. In addition, in the case of copper-cobalt-nickel alloy plating, a printed circuit having a circuit width of 150 μm or less can be etched with a CuCl ₂ etching solution, and alkali etching can be performed. As the alkaline etchant,
For example, liquids such as NH ₄ OH: 6 mol / liter; NH ₄ Cl: 5 mol / liter; and CuCl ₂ : 2 mol / liter (temperature: 50 ° C.) are known.

[0019]

EXAMPLES Examples and comparative examples will be described below. Electrolytic copper foil (JTC: manufactured by Nikko Gould Foil Co., Ltd.) with a roughened surface roughened with copper-arsenic and plated with brass
The rough surface was subjected to a roughening treatment under the following condition range: (Sample 1: Comparative Example) As a conventional example containing arsenic, copper sulfate (pentahydrate) 100 g / l, sulfuric acid 100 g / l
And an aqueous solution containing 3 g / l of arsenic acid at 30 ° C. as an electrolytic bath.
Plating was performed at 0 A / dm ² for 10 seconds. (Sample 2: Comparative Example) Copper plating was performed under the following conditions: Cu: 15 g / liter H ₂ SO ₄ : 50 g / liter pH: 3 Temperature: 30 ° C. Current density D _k : 50 A / dm ² hours: 3 seconds (Sample 3: Example) Cu-Co-Ni plating was performed under the following conditions: Cu: 15 g / liter Co: 5 g / liter Ni: 5 g / liter pH: 3 Temperature: 45 ° C. Current density D _k : 25 A / dm ² hours: 3 seconds (Sample 4: Example) Cu-Ni plating was performed under the following conditions: Cu: 7 g / liter Ni: 15 g / liter pH: 3 Temperature: 32 ° C. Current density D _k : 20 A / dm ² hours: 3 seconds

For these samples, after chromate rust prevention treatment, the samples were laminated and adhered to a glass cloth base epoxy resin plate, and the peel strength (kg / cm) and the heat peel strength deterioration rate (%): 180 ° C. × 2 days, Hydrochloric acid resistance deterioration rate (%): immersed in 18% by volume hydrochloric acid aqueous solution at room temperature for 1 hour, surface roughness, color tone, oxidation resistance: baking (determined visually) at 180 ° C. for 30 minutes, and adhesion amount were examined.

The results are shown in Tables 1, 2 and 3.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

Sample 1 had a high peeling strength due to a strong roughening effect, but had poor hydrochloric acid resistance as compared with the others. Also, the use of arsenic is environmentally unfavorable. In Samples 1 and 2, good heat resistance was not obtained, and discoloration was remarkable due to aging. The decrease in heat resistance is presumed to be due to the migration of copper to the interface and the decomposition of the epoxy adhesive. Samples 3 and 4 exhibited good heat and oxidation resistance. This is presumably because the diffusion of copper was suppressed by alloying.

[0026]

By providing a roughened surface layer made of a Cu-Ni alloy or a Cu-Co-Ni alloy on the glossy surface of an electrolytic copper foil whose roughened surface is normally treated, excellent heat resistance and oxidation resistance are obtained. Thus, an electrolytic copper foil suitable for use as a copper foil for a printed circuit, particularly an electrolytic copper foil for an inner layer of a multilayer printed wiring board can be obtained.

Claims (3)

[Claims] 1. A glossy surface made of a Cu—Ni alloy or Cu—Co
-An electrolytic copper foil provided with a roughening layer made of a Ni alloy. 2. The electrolytic copper foil according to claim 1, wherein a coating layer made of a Cu—Zn alloy is provided on the roughened surface. 3. The electrolytic copper foil according to claim 1, further comprising a Cr-based antirust layer on at least one surface.